Road milling machines, also known as cold planers, may be configured to scarify, remove, mix, or reclaim material from the surface of bituminous, concrete, or asphalt roadways and other surfaces using a rotatable planing tool mounted on a frame. The frame may be mounted on a plurality of tracks or wheels which support and transport the machine along the roadway surface.
Typically, cold planers may also include a plurality of lifting members positioned near the front and rear of the frame. The lifting members may be adjusted between extending and retracted positions to control the depth and shape of a cut by raising or lowering the frame and rotatable planning tool.
U.S. Publication No. 2009/0108663 (“Berning et al.”) published Apr. 30, 2009 is an example of prior art related to positioning a road milling machine parallel with the ground. While Berning et al. discusses controlling the parallelism of the machine after a change in milling depth, it does not disclose actively managing this parallelism during the descent or ascent to the new milling depth. A better design is needed that actively controls the extension or retraction of the rear legs during the change in milling depth.